That's an interesting question. I would try to explain it as follows:
The key to the directionality of a shotgun microphone is that the sound
waves arriving from the side reach the capsule at the end of the tube via
various path's (through the holes or slits along the tube). Due to the
different path lengths, the various sound components will be delayed agains=
t
each other. Sound waves entering the tube via slits close to the capsule
arrive earlier than those entering the tube via more distant slits. These
time delays cause phase cancelations that attenuate the sound.
On-axis sound reaches the capsule via one single path only (along the axis
of the shotgun) and therefore the attenuating phase cancelations do not
occur.
Usually, all phase cancellations are frequency-dependent. Therefore, the
manufacturers try to arrange the holes along the tube in a very special
pattern in order to minimize the off-axis coloration.
Regards,
Raimund
> All,
> I don't understand how a shotgun microphone attenuates the sound
> >from the side. Is it possible to put that function into layman's
> terms for me? I know that the longer the shotgun tube the more
> efficient it is. My thoughts are that sound waves near the axis are
> allowed to pass down the tube with less interference than waves from
> the side. Perhaps the tube causes the wave to be reflected more
> often when it enters from the side? If the side wave is being
> redirected within the tube why doesn't that effect the waves on axis?
> 1GDW
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________________________________________________________________________
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"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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